Method and apparatus for grinding and polishing ligatures



Aug. 15, 1944. wA A, cox 2,355,907

METHOD AND APPARATUS FOR GRINDING AND POLISHING LIGATURES Original FiledJuly 24, 1940 2 Sheets-Sheet l AQ A A A%.$\\

Aug. 15, 1944. Y w, A, cox 2,355,907

METHOD AND APPARATUS FOR GRINDING AND POLISHING LIGATURES original FiledJuly 24, 1940 2 sheets-sneer 2 Patented Aug. 15, 1944,

METHOD ANDAPPARATUS FOR GRINDING y Y AND POLISHDIG LIGATURES Walter A.Cox, Chicago, Ill., assignor-to Johnson 85` Johnson. a corporation ofNew Jersey Continuation of application `Serial No. 347,280, July 24,1940. This application November 12, 1943 Serial No. 509,968 J 9 Claims.(CL 51-103) `My invention provides for polishing surgical catgut totruly circular section and uniform gage throughout its effective lengthso that a strand having the maximum ldiameterallowable `under governmentand Aother authorized specifications,

throughout its 4le`ength'wil1 havegreater tensile strength than a strandwhich ,varies as much as .003" in diameter at one or more points, thetolerance permitted under such specifications.

The polishing Vof surgical catgut which has a diameter of the order ofthousandths'of inches only is a necessary even though difficultoperalprone to slip and knot slippage in surgic tion Vdespite the factthat. as heretofore conducted, it tends to loss of tensilestrength.Unpolished catgut is used little;n if at all.. because it is difficultto draw through tissue without serious injury to thelatter. Handpolishing `has its disadvantages and yet catgut which has been handpolished under the best conditions shows a lower lo'ss of tensilestrength than catgut that Ahas been polished in the conventional orso-called European machine. In that machine an abrasive disk passes upand down the length of the strand.-

of catgut and it is quite probable that, the heat thereby generatedaccounts fonthe loss of tensile strength. Bethat as itv may, it is afact that catgut polished in theconventional manner by hand or bymachine has a surface texture such that when the'catgut is knotted theknots are l work can be quite serious. i

Surgical catgrttis fabricated from ribbons of animal tissue or fiberstwisted togetherV in more or less helicalY form. Hence, the raw stringis generally marked by relatively thick and thin sections with noparticular order of arrangement and by surface irregularities;4 Thebreaking strengthof a A'ligature otherwise sound Vis definitely governedby its 'minimum cross-section.

In a general sense `the conventional polishing takes no account of thisbeing directed simply to the removal of humps and other surfaceirregularitiesV in the doing of which it not infrequently cuts or tears.the tissue and removes portionsof the surfacey atlthe hollows as wellas at the humps, at any rate, the cross-section of ,a conventionalv*polished strand of catgut is notuniform/and not truly circular. l f

Prior to my invention no serious eflort'was` made to pregage therawstock in order to determine the useful or effective minimumcrosssection and to polish the string `to a truly circular cross-sectioncomparable therewith. So far as I am advised, the practice is to polisha bunchof i raw. stringsv either by hand application of the ll wherein:

abrasive-or by spinning the strings between abrasive surfaces whilegrasping them endwise. The

best hand polishing often results in flat strings and, yet, handpolishing is preferred to the con.- ventional machine polishing becauselabor is cheaper than machine work, there is lessspoilage,'no pronounceddifference in the appearance `of the4 respective products. less loss intensile strength, and withal the operation is cheaper.

It has been reportedthat thegreater part of surgical catgut productionin this country is either partially or wholly hand polished and that thetensile strength of American catgut is far above that of foreigncountries. And, yet,v because ithas not heretofore been possible Vtoproduce a strand of catgut of truly circular section and uniform gagethroughout its effective length, the variousgovernment agencies in theirspecications relative to the purchase of surgical catgut, allow atolerance of .003" within a given gage. The same tolerance is specifiedin the U. S. Pharmacopoeia which became oilicial in September l1939.

Principal objects of the present invention are to polish strings of thenature indicated, that is 'relatively thin limp strings incapable ofsupporting themselves in .short lengths such as lengths, of a fewinches, and to do so rapidly, economically and eciently toa truecircular section in such way as to make available for surgical and otheruses practically all of the raw stock in all of its inherent strength;in such way that there will be no Aforeign inclusions of the nature ofgrit; and in such way that the surface texl ture will be normal to themajor axis of the string and fof Vpronounced smoothness; to provide forpre-gaging the rawstring and selecting for polishing units thereofaccordingto the respective minimum cross-section; to provide forpolishing such units by single pass through the grinding throatof amodified centerless grinder and in such way as to eliminate heat andother factors having a tendency to, impair the tensile strength of thestringi and to provide a method and means fuor achieving such objectsand forproducing the Y novel strand of surgical catgut of my invention.

The nature, characteristic features and scope of the invention morereadily will be understood from the following description taken inconnection with.' the accompanying drawings, forming a part hereof allconstituting part of this application for Letters Patent whichapplication is `a'. continuation of my earlier led application SerialNumber 35,280, led July 24, 1940, and

ticularly showing how y normal to the axis; y

Y Fig. .'7 isa -diagrammatic layout for practicingV V;my method ofpolishing. surgical catgut;

accordance withthe invention so that the perimeter is truly concentricto the axis throughout the` length thereof; l

Fig. 4 is a section on line 4 4 of Fig. 3 showing the smooth andsubstantially enamel-like surface of the polished string;

Fig. 5is a reproduction of a photomicrograph of a strand of surgicalcatgut which has been polished in the conventional way showing that thelands or grooves resulting from thev conventional longitudinal polishingare parallel to the axis, and also showing the presence ofnap;

.Fig 6 is a View similar to Fig. 5 of a string polished according to mypractice and more parthe surface texture isv vFigli isa sectionaldetailof the layout; and Fig. 9 is asectional detail of the ejector.

In` the preferred practice of vmy invention I first` pre-gage.the stringof raw stock and, predi- Y cated onthe results of the ypre-gaging,divide the string into unitsk for :polishing and ultimate accurateclassification as #A1, #2, #3, etc., the polishing being accomplished bya modified centerless grindingor'polishing operation whereby the stringunit at one pass is polished to truly circular section and uniform gagethroughout its-elfective'length without impairment of tensile strengthand in such way that the surface tex- Ature resulting from theunavoidable abrasion marks. will be normal to the axis.

The conventional centerless` grinderor, more accurately stated, theconventional instrumentalities for conducting the stock to and away fromthe grinding throat are incapable of contributing toward accomplishingthe ultimate purpose of my invention. Howeverj'under my system ofcontrol of-feed-and delivery -Which is preferred in a complete system orapparatus it follows that .oncethe grinding throat is adjusted foroperation on units of a certain classification, it is possible inacommercial way, that is to say', rapidly, efficiently and economicallycontinuously to polish the units to truly circular section and uniformgage. The control comprehends apush and-pull operation, andinstrumentalities for Ycarrying it into effect whereby units, other thanunt or rejected units, are pushed or impelled a'nto the grinding throatand after polishing pulled therefrom, Vthe pushingand pullinginstrumentalities and intervening work supports operating to maintaintension on thestring unit so as to minimize the building up of resistingforces and particularly torque in the string. Undermy system ofpre-gaging. classification and control I can, by asingle pass grind andpolish surgical catgut to an uniform circular section, the totalvariation being substantially not more than 0.0005". 1

It is a merit of the invention that the pushing or feeding systemcomprehends a'luid conveyer to handle the string units to be polished.Such conveyer may be either of the pneumatic or hydraulic type. It ispreferred, however, to employ a hydraulic conveyer or injector becauseit lends itself to that part of the invention which provides for the useof a cooling medium to prevent or substantially inhibit the generationof ing or injecting instrumentality is of the hydraulic type, theejector will, by, preference, be

. of the' pneumatic type in order to substantially the machine cycle.

effect the drying of the polished units during It will be understoodthen,`having reference to Pig. 1, that the raw or unpolished strand 5 ispre-gaged and marked according to its variable areas of minimumcross-section for ultimate division and classification of unpolishedunits or sections. For example, assuming that the string is twenty feetlong, it is pre-gagedinto say, four 5-foot sections and, since the'minimum diameter is the factor that determines the size to which thestring is to be ground and polished, two sections ,may serve for #lstring andthe other sections for #2 and #3, respectively... Fig. 2 showsin contrast broken sections of the pregaged unit having a maximumdiameter vof .028" and a minimum diameter of .0235". Such and otherunpolished units are separated according to classificationfand it willbek evident that thenot contain'inferior material, has .been properlymade and dried, and so long as no plies are cut in the polishingprocess. It follows that if a polishing process for the production of,say, #2 sutures is set up so that the averagesize ofr the suture is0.021 (the upper limit of #2) `and if, further, the sutures producedhave a maximum totalvariation of 0.003", then the strength of such asuture will be determined by the strength of its minimum section, i. e.,onewhose diameter is`0.0195", and the .maximum size of the suture willbe 0.0225, or a size equivalent to a #3. In other words, the resultantsuture will be an oversize #2 with the strength of light #2. If themaximum total variation in diameter were reduced to, say, 0.0005, thenthe diameter would range between 0.02075 and 0.02125, Vthe strengthwould be determined `by the 0.02075" section and the whole. suture wouldbe sized as a full #2. From this it follows that a decrease in thediametric variation of .a suture, while notconstituting an improvementin the inherent strength of the material should, nevertheless, improvethe effective strength of any given size. Demonstration has proved thisto be the case. [t may be mentioned that variations of from 0.003" to0.005" are usual in material polished by hand or by the conventionalmachine method. A #2 string is a relatively large size string and,hence, the percentage increase in minimum area is even more marked inthe smaller sizes.

Figs. 3 and 4 show the blank of Fig. 2 polished to an even and uniformdiameter and having a surface devoid of nap and smooth andlsubstantialiy venamel-like as indicated at 6.

Fig. 5 shows a string that has been ground and polished intheconventional way and characterized by the non-uniformity of itsdiameter, by the presence of lands or grooves 1, due to the".'longltudlnal polishing, ranging parallel to string axis, :and`further `characterized by the presence of'fuzz or nap.

be Jair, water;V lard'oil,

j am Vthe guide 'than the hydraulic type'. :principally to provideforthe (Fig. v6Y shows a'sir'nilarstrin'g grroundby the VL'n'iethod ofmyinvention, characterized by its u'ni- "form diameter, its smoothsurface, and by the V@fact that ltssurface texture is normal to its axis:as-indicatedva'tl. o o

Referring to -the diagrammatic layout, Fig. '7,

the numeral fil indicates a grinding wheel and l0 Laregulating-wheelcustomary in a so called-cen- .'fterless :grinder andrelatively ladjustable tofpro- #avide `a Vvariable grinding throat II-'The `cus- :gtomaryigrindingthroat is modifiedtoprovide suitableworksupports orinstrumentalities l2 `which"participate in *the adjustmentstated for .determining the gage of polishing `and. toi sustain 4thestring'units against whipping ,or vibrating pro'priate wayand having anoutlet or nozzle lI5 Y Vwhich "feeds the` units 'to the grinding throat.

' Nozzle I5' may be any appropriate type of Vfluid `irriector,-forexample, the injector shown in Fig.

Shaving an axial bore i6 serving as a vstring or -rwork conduit, and aport il forthe admission r:of a;highzv'elocity stream offluid.V The uidVmay etc..bu,t, as beforeistated, v"I prefer to usea cooling mediumsuchas a hy- ,drocarbonl liquid or gas. 'ls an -excellent coolingmedium,V is effective to 'swash :away the-polishing debris and beingvolatilemakes-for rapid drying of theV polished unit.

For example, "Cumol A.coolingsubstance of theV type indicatedfconfersupon Athe polished `string a'V substantially A.smooth and somewhatenamel-like 4also iseffective asasterilizing agenti surface, and

AAt-fsome point conveniently located inthe -string `guidecr conduit" I 3there is provided, as -at 1,8,..any` appropriateV form" of gage orotherconventional deviceffor rejecting lumpy or defec-.tives'tringunitsor for indicating the presence of units which,fifpermitted to pass that point, might or the grinding throat and sointerrupt the'continuity of the machine operation.

-Intermediate the rejecting station and the in- .Jector is a suitablecontrol or pressure reducer 1I-S for regulating the action of theinjector.

On` the delivery side of the grinding throat there is a. stringreceivingand pulling device comprising a blastor ejector nozzle'Zll of anysuitable well-,known type communicating with a discharge conduit 2|; Itwill be understood that nozzle .20 maybe regulated in anyl well known Y`manner to vary the pressure volume of the air or other Vfluid medium;In spite of lowere'fflcienc'ies the ejectorispreferably of the pneumaticrather Thischoice is made polished ligature as itpassesthrougntheejector,

vthus eliminating the necessity of a separate drylng` operation afterthe grinding orpolishing operation. Actually the drying takes place intwo .distinct phases. As the rapidly rotating string .passes the gapbetween the injection and ejection tubes, the excess' coolant is removedby centrlfugal force. .The vremaining surface coating of vcoolant isevaporated by the action of the air blast in the ejector nozzle. TheVejector is so' designed and arranged that there is a slight posi- Ytivepressure at the inlet. If the pressure at that point were negative,part of the coolant-laden atmosphere in the grinding throat would bedrying the ground or" d rawuolf, the evaporating` efficiency of thenozzle Vwould be reduced to a -pointfwhere :wet-.strings would result,Vand a lcertain lamounto'f coolant would be continuously lost.

It will be understood that-.duringfthe .polishing operation the rotationand travel ofV thestring are controlled by wheel action within theA.grinding throat and in the. preferred form of apparatus by thecoordinate Vactionof the propelling and pulling instrumentalitles inconjunction -with the o `Work supports which maintain-the :centerline ofgrinding or polishing. `The leading end `iof-:the

V whilebeing axiauylfed atrelatively highspeed A-zfandwhile rotatingathighz speed. Y At i3 is indi- 'fcated a tubular conduit havinganirilet I4 to which Athe string units are -directed in any ap- "stringbeing fed followsclosely the trailinglend Y of thestring Vbeingpolished. While itis `occupying Vthe grinding throat. the .string isVunder :pushingjaction ofitheinjector and pulling-,action of the"ejector when these preferred finstrumentalities are used. One effectofthis: duringeextreme [instances of polishing is to prevent4 the'stringfrom stallingin thegrinding throat shouldit be 4one that has passedinspection and yet containsV an undersize section of a length greatervthan the Y length of thegrinding throat, i. e.,' afsectionwhose havedevised `a method and means `whereby-sur- 'diameter isless thanthat of,thegrindingthroat It will be apparent from .the foregoing `thatIgicalsutures are `pre-.gaged and sorted: .for -polishing and'arepolishedto true circular section and uniformity'oflgage, thetolerance or..tota.l

' suture.

variation being substantially not moreuthan 0.0005" in contrasttogovernment and other authorized tolerance'of .003". p

` The polishing `is effected funder..;conditions Moreover,.

which inhibit loss of. tensile strength; astrand `of catgut having .themaximumdiameter, allowable under government or other authority.uniformly throughout its-length will have greater ltensilestrength thana. strand which varies as much asA .0035 in diameter -at one or morepoints.

The precision productoffmy invention makes for accurate and dependablelabelingsothat the surgeon need no longer be under .apprehension that heis working with a wrong size or `doubtful Heretofore, and prior to myinvention, surgical catgut labels afforded no laccurate guide as tosizeand strength. f In short, thesurgeon could but ask for acertainnumber, for example, #2, and he might and might not get a suturestrong enough for his purpose because .003"

Y tolerance is .allowed in each sizeand that variation'between the feedline and the grinding throat and effective to supply wet stock to thevgrinding throat, and an ejector of the dry type on the other side ofthe grinding throat and effective to receive and dry the polished stock.

2. In an apparatus for polishing fiexible strings t0 insure a uniformlyround section and apol- V ished surface characterized by ridges normalto the lengthwise axis of the strings, the combination comprising agrinding wheel, Va regulating wheel, a string support providing agrinding throat, and aligned fluid injector and ejector del vices forcontrolling the movement of the strings v 'abouty itsv longitudinalaxis.

vancing said element longitudinally through said` zone, restricting saidelement while in said zone Y against any appreciable movement out of its'longitudinal path, and grinding orv polishing the element fwhilerinsaidzone 'and as it is rotated 4'. The metnqdffof 'lnaiicllingY al'imp,pliable;

Y .Y Vcord-'like element,fsuch as a suture, to render it substantiallyuniform in diameter by grinding or polishingwhich method includesconveying -s'aid'eleme'nt by the action of a bodyof fluid polishingwhich method includes conveying said element by the action of a body offluid surround- `ing said element and moving in a direction to orpolishing the element while in said zone, and Y simultaneously conveyingsaid element away from said zone and drying said element.

' 8. The method of grinding an individual length 'of a cord-like elementto render said Yelement substantiallyfuniform in diameter which methodincludes the steps of continuously advancing an individual length of alimp pliable cord-like element, suchfas a. suture having a diameterofthe order of thousandths of an inch and which when Auntensioned isincapable of self-support, longitusurrounding said element and moving ina direc'- tionto convey the 'element longitudinally toward a grinding-orpolishing zone, continuously ad- VanCin'g-'SaidfeIementlongitudinallyvthrough said zone; restricting said element while in saidzone :i against"Y any appreciable-movement out of its longitudinalpathjgrinding or polishing the ele- 'ment while in said' zoneandconveying said elemerit longitudinally by the'action `of a body of 'uidsurrounding said element and movingin a direction away from said zone.

r5`1-The"method `of handling a limp, pliable, cord-like element, such asa suture, to render it substantially uniform in diameter by grinding orpolishing which-method includes conveying said elemen'tfby `the actionof a, bodyrof liquid surrounding said element and moving in a directionto convey-the element longitudinally toward a grinding or polishingzone, continuously advanc- -ingwsaidelement longitudinally through saidzone, restricting said element while in said zone against anyappreciable movement out of its longitudinal path and grindingorpolishing the element while in said zone and as it is rotated about .itslongitudinal axis;

/ eiThe method of handling a limp, pliable, cordflike element, such asavsuture, to render it substantially uniform in diameter by grinding or.

gitudinal path, grinding or polishing the elementV while in said zone,and conveying said element longitudinally bythe'action of a body of airsurrounding said element and moving in a direc- Vtioniaway from saidzone.

7. The methodof handling a limp, pliable cord-likeelement, such as asuture, to render it substantially uniform in diameter by grinding ordinally through a grindingV or polishing zone, positively restrictingsaid element `while in said zone against any appreciable movement out oflits longitudinal path, and lgrinding or polishing the surface of saidelement transversely to its longitudinal'axis whileV rotating theelement about said axis, the longitudinal movement through the grindingzone and the rotational movement of said element being effectedsimultaneously and by engagement vof the grinding or polishing mediawith that portion of said element in the grinding zone of a diametergreater than will p ermit free passage through said zone, vthe ends ofsaid limp element being maintainedV free so as to permit saidlongitudinal and rotational movement.

9. The method of handlingv an individual lengthof a cord-likeelement torender said suture substantially uniform in diameter by grinding orpolishing which method includes the steps o f conveying an individuallength of a limp pliable cord-like element such as a suture having adiameter of the order of thousandths'of an inch and which whenuntensioned is incapable of selfsupport, longitudinally toward agrinding or polishing zone, continuously advancing said individual-element'longitudinally through `said zone, positively restrictingsaidvelement while in said zone against any appreciable movement out of4its longitudinal path, grinding and polishing said element transverselyto its longitudinal axis while rotating said element vabouttitslongitudinal axis, and conveying said Velement longitudinally away fromsaid zone, said limp element being supported exteriorly of and adjacentboth ends of said zone to facilitate its longitudinal movement as it isVconveyed toward and away from said zone, the ends of said element beingmaintained free so as to permitthe longitudinal movement through thegrinding zone and rotational movement of the element in said zone' whichmovements are effected simultaneously by engagement of the grinding orpolishing media with that portion of -the element within the grindingzone and of a diameter greater than will permit free passage throughsaid zone- WALTER. A. COX.V

